HARK/HEARKEN

One old use of the word “hark” was in hunting with hounds, meaning to turn the dogs back on their course, reverse direction. It was this use that gave rise to the expression “hark back.” It refers to returning in thought to an earlier time or returning to an earlier discussion: “That tie-died shirt harks back to the days we used to go to rock festivals together.”

The expression is not “hearkens back.” Although “hark” and “hearken” can both mean “listen,” only “hark” can mean “go back.”